The short answer to your question is, "YES". More detail below.
I used vi almost exclusively from about 1980 to 1991. The only time I didn't use vi was when I was dealing with a minimal install of Unix that was too small to include vi, so I had to drop back to ed which is the minimal subset of editing functionality that the original vi was built on top of.
From about 1985 on, other programmers where I worked were constantly singing the praises of emacs. But every time I'd try to learn it I wouldn't get very far. I'd spend an hour going through the emacs turorial (C-h t) and by the end of it all I'd know would be how to insert and modify text and move around the screen. I could do so much more with vi than what I'd learned in that hour with emacs that I couldn't make the switch. Three months later I'd find time to spend another hour and I'd end up going through the same material. Emacs has a Learning Curve with a capital "L". It wasn't until I was doing a contract where everybody else used emacs that I eventually decided I needed to devote more than an hour at a time to learning it. After spending a little over a day doing nothing but working through the tutorial and the included documentation, I finally got to the point where I could do things with emacs that I couldn't with vi. From then on, I've never wanted to go back. I can still type vi commands in my sleep, but I can do so much more with emacs.
Understand that I'm comparing emacs and vi, not vim. I've never learned the extensions that vim has added to vi, and it's likely that many of them are features copied from emacs. If so, and if you're already proficient with vim, emacs may not hold as many advantages for you.
When you use emacs, everything's treated as text. This means that you can manipulate any data in any buffer with pretty much the same commands. And in cases where a buffer's in a mode where some of the standard commands are unavailable, you can copy text to another buffer running in fundamental mode and use the standard commands there.
Emacs provides a multi-"window" environment displayable in on a character-cell terminal. In the days before bitmapped graphics and real windows, emacs was written to simulate window-like behavior using nothing but ascii characters and cursor positioning. You're probably thinking, "That's ancient history. Why should anyone care about that today?" I still use that capability every day. I use a webhosting company that allows me SSH access. So I can log into a Linux host across the Internet and run shell commands. While that's pretty powerful, it's far more powerful to be able to divide my terminal emulator up into "windows" using emacs, run shells in several of those "windows", edit files in other windows, and view and edit directories in still other "windows".
Actually, when I said "window" in the previous paragraph, I really meant "buffer". Emacs' character cell emulation of windows is a way of dividing up the screen real-estate. An emacs buffer is associated with content (a file, a bash shell, a directory, arbitrary text not associated with a file, etc.) which may or may not currently be displayed. To view what's in a buffer, you pick a window and tell it what buffer you want to see. So you can be working on way more things than you have space on the screen to display. It's roughly analogous to what you do in a modern bitmapped-graphics GUI when you iconify/de-iconify a window.
I've already alluded to the fact that you can run a shell inside an emacs buffer. You can have as many buffers running shells as you like. You can copy and paste text back and forth between a shell buffer and a text file, or compare a portion of text between a shell buffer and a text file using the exact same keystroke sequences you would use to copy text or compare text between two different text files. Actually, this is true for most types of buffers, not just shell buffers and buffers associated with files.
When you use emacs' command to open a file, but what you've selected is actually a directory, the buffer runs in dired (directory editor) mode. In this mode, a single keystroke will open whatever the cursor's currently pointing at, be it a file or subdirectory. A buffer in dired mode is a file manager - a character-cell terminal oriented analog to Finder on the Mac or Windows Explorer.
One of the emacs functions I use almost constantly is "compare-windows". I greatly prefer this to command-line "diff" or GUI comparison tools like what's built in to Eclipse. Diff or Eclipse compare entire files, and show you which lines differ. But what happens when you have two different lines that look very similar? Consider the following:
What's the difference between this line and the other?
What’s the difference between this line and the other?
How long would it take you spot the difference? (Hint: ASCII and Unicode apostrophe look pretty much alike.)
Unlike diff and Eclipse, which just show the lines that differ, emacs' "compare-windows" function is interactive. You position the cursor in each of two side-by-side windows at a point where the window contents are the same. Run "compare-windows", and the cursor in each window will move to the first character that differs. Reposition the cursor in one of the windows to the point where it's the same as the other window, and rerun "compare-windows" to find the next difference. This makes it easy to compare subportions of files.
Another thing I regularly use "compare-windows" for is comparing checksums. Many software projects distribute a tarball of the application on a page that also includes an MD5 hash of the tarball. So, how do you compare the MD5 hash on the distribution page with the MD5 hash computed from the downloaded file. Emacs makes this trivial.
First copy the MD5 hash from the webpage into a new emacs buffer. Then, after downloading the .tar.gz file, run:
md5sum downloadedfile.tar.gz
in a shell buffer. With those two buffers displayed in side-by-side emacs windows, position the cursor in each window at the beginning of the checksum and run "compare-windows". If they're the same, the cursor in each window will be positioned at the end of each checksum.
In the previous point, I gave the example of running "compare-windows" on the lines:
What's the difference between this line and the other?
What’s the difference between this line and the other?
"compare-windows" will leave the cursor positioned on the apostrophe in each line. So, now you know which characters differ. But what characters are they? Type the two keystroke command CTRL-x =, and emacs will display the character, its ascii value in octal, decimal, and hex, the character offset from the beginning of the file, and the character offset from the beginning of the line. Since ASCII is a 7-bit encoding, all ASCII characters have their high-order bit turned off. Once you see that the value of the first apostrophe is 0x27 and the second one is 0x92, it's obvious that the first one is in the ASCII character set and the second one is not.
Emacs was one of the first IDEs, perhaps the very first one. It has modes for specific languages. I find them handy for imposing consistent indentation on my code to make it more readable. There's also built-in functionality for compiling and debugging code. I don't use the compiling functionality that much because when I was writing for a compiled language like C, I was used to doing that at a shell prompt. The debugging functionality was very nice for C and C++. It integrated gdb with the editor in such a way that you got pretty much the same functionality as the debugging capabilities now in Eclipse, but didn't waste screen real-estate the way modern GUI-based IDEs do. Theoretically the debugger integration should be easy to make it apply to virtually any other language, but I haven't checked to see what other languages it works with nowadays.
Emacs allows you to create macros by telling it when to start remembering what you're typing and when to stop. This is extremely powerful for tasks you frequently do.
Emacs is infinitely extensible if you know Lisp. But even though I've never learned Emacs Lisp, I still find Emacs one of the most powerful tools I've ever used.
Emacs key-bindings. I'll be the first one to admit that Emacs key-bindings suck. But it's so much more powerful than anything else I've used, that I'm willing to put up with the key-bindings.
In a humorous vein, years ago Emacs' author Richard Stallman (also originator of the GPL, founder of the GNU project and founder of FSF) lampooned those who treat vi vs. emacs as a holy war. He invented the character "Saint IGNUcius" of the Church of Emacs. In that guise, Stallman commented, "Sometimes people ask me whether it is a sin in the Church of Emacs to use the other text editor vi. Well, it's true that vi vi vi is the editor of the beast, but using a free version of vi is not a sin, it's a penance." (See http://stallman.org/saint.html. There's also a cute photo of him, but since I'm new to StackOverflow, it won't let me post more than one URL. So go to the same domain, but fetch the file saintignucius.jpg)
